Reliability of manufactured electronic components is a critical consideration for most electronic component manufacturers. Many manufacturers conduct testing of electronic components as a standard step in the manufacturing process. Such testing may range from testing of a statistically insignificant percentage of the total number of components produced selected periodically at random to one hundred percent testing of each and every electronic component produced.
In any event, testing can be directed toward two basic goals. One goal is to cause the component to fail by subjecting it to extreme conditions which will simulate the environmental conditions to which a component is expected to be exposed on an extraordinarily accelerated time period. An example of such testing is an accelerated duty cycle test in which the component is subjected to a number of duty cycles far in excess the number which the component will see during its expected life in a very short time period. Another goal is to subject the components to screen testing which is designed to turn marginal defects into detectible hard failures. Such screening is not intended to find design defects or to qualify a component, but is a process used to detect and eliminate defects during the manufacturing process.
Such screen testing is typically accomplished by carefully selected environmental stress screening procedures. These environmental stress screening procedures include thermal and dynamic screening which is developed for specific components.
Printed wiring boards (PWB) are used in most devices which incorporate electronics. Such devices frequently have numerous PWBs electrically connected to each other. PWBs carry individual electronic components electrically interconnected on the board. In a device which includes several PWBs, the premature failure of the PWB or a component carried by it, can result in the need to replace the PWB after the device has been sold to a customer and put in use, or result in the need to replace the entire device due to damage caused by such failure. In order to avoid such problems and risks of failures, PWBs are frequently screened to detect marginal defects prior to the board's individual sale or incorporation into an electronic device which is then subsequently sold to a consumer or user.
One effective method of environmentally stress screening a PWB is to subject it to dynamic vibrations. In order to do so, PWBs are typically mounted in fixtures which are secured to shaker tables and subjected to various vibrations induced by the shaker table. In order to incorporate such screening as part of the manufacturing process, it is necessary that the fixture allow easy and quick insertion and removal of the PWBs being screened. Additionally, since most PWB manufacturers boards vary in size and componentry, it is necessary for the fixture to be easily adaptable to accept various boards.
To accomplish this, the industry has made use of adjustable fixtures having substantially parallel opposing faces with vertical grooves formed therein. These grooves or notches as are known in the art are aligned with the notches on the opposing face. The notches used heretofore have had an included angle of ninety degrees. Such notches, however, present a problem in that they are not readily adaptable to the wide range of PWBs being manufactured.